(1) Field of the Invention
The present invention relates generally to piston-cylinder measurement systems and, more particularly, to a non-invasive piston-cylinder extruder measurement system and method of use.
(2) Description of the Prior Art
It may be desirable to measure fluid flow into or out of a piston-cylinder assembly such as a piston-cylinder extruder. An off-the-shelf impeller type flow meter may be utilized for making flow measurements in a piston-cylinder extruder if the extruder operates with low viscosity liquids under low pressure. However, for use with high viscosity, high pressure liquids, and for use with certain types of explosives, impeller type flow meters have significant problems. An impeller type flow meter sensor not only reduces the maximum flow rate in the extruder tube, but also creates a “pinch point”, because of the flow meter's moving impeller in the presence of the explosives.
Non-invasive flow meters may be found in the market, but they do not accurately sense flow rates of high viscosity fluids such as explosives in the extruder tube. For this type of measurement, errors may arise for various reasons such as, for example, a small diameter extruder tube, inconsistent fluid density, and/or mechanics of the particular type of flow meter.
The following U.S. patents describe various prior art systems that may be related to the above and/or other types of extruder measurement systems:
U.S. Pat. No. 4,517,145, issued May 14, 1985, to Knopf, discloses an improved extrusion die employing proximity sensors to directly measure the actual die gap during extrusion. The proximity sensor may be a capacitance-effect, or optical-effect sensor. Manual and automated closed-loop methods of operation are also disclosed.
U.S. Pat. No. 4,680,152, issued Jul. 14, 1987, and U.S. Pat. No. 4,728,278, issued Mar. 1, 1988, to Capelle, discloses a method for monitoring deviations in the dimensions of profile strips during production, as is an apparatus suitable for carrying out the method. The profile strip is formed from one or more rubber or thermoplastic material mixtures which are fed from one or more extrusion devices through nozzles into a common nozzle in an extrusion head. Pressure and temperature measuring means measure the extrusion pressure and temperature of each mixture. The profile strip thus produced then passes over weighing device which measures its weight per unit length. The measured value is transmitted to a regulating or control device and compared with a desired weight per unit length. When a deviation is ascertained, the regulation or control device which is also operatively connected to the pressure and temperature means and to adjustable drives for each extrusion device, compared the measured extrusion pressure and temperature values with desired values and adjusts the drive of one or more of the extrusion devices to cause the measured pressure and temperature values, and hence the measured weight per unit length, to be restored to their desired values.
U.S. Pat. No. 4,695,236, issued Sep. 22, 1987, to Predohl et al, discloses an apparatus for continuous extrusion of a plastic laminate that has at least two extrusion screw presses, an accumulator block, a transition unit, and an output die, from which the plastic laminate product is extruded. The accumulator block has a combining channel or canal therein which is fed by the extrusion screw presses. This combining canal is connected by way of the transition unit to the output die. The combining canal preferably has a rectangular cross section with rounded corners and at its upstream end is directly connected to a first extrusion screw press by way of a connecting canal coaxial with the combining canal. Downstreamwards below the connecting canal is found at least one input metering slot connected to the combining canal at one end and through a connecting apparatus at its other end to an additional extrusion screw press, this input metering slot lying between an input plate and an adjusting bar guided in an adjusting bar recess. The input metering slot extends over a rectangular side of the rectangular cross section combining canal, is directed slantingly downstreamwards, and opens into the combining canal. The adjusting bar has an adjustable beveled portion fitting into the combining canal and is adjustable perpendicular to the input metering slot in the adjusting bar recess so as to meter the flow of thermoplastic material from the additional extrusion screw press.
U.S. Pat. No. 4,740,146, issued Apr. 26, 1988, to Angelbeck, discloses an apparatus for producing plastic pipes by an extrusion process in which the wall thickness of the plastic pipe is controlled by the takeaway speed at which a soft plastic pipe is removed from a metal sizing sleeve. To measure the wall thickness of the soft plastic pipe advancing through the sizing sleeve for regulating the takeaway speed, a transducer emits ultrasonic sound through a plastic transmission line mounted in or on the sizing sleeve and interposed between the transducer and the plastic pipe. The time interval between the emission of a sonic pulse by the transducer and the detection of a reflected sonic pulse from the inner wall of the advancing soft plastic pipe is a function of the wall thickness of the plastic pipe in a soft plastic state.
U.S. Pat. No. 4,744,930, issued May 17, 1988, to Twist et al, discloses an extrusion process is controlled by feeding the material to be extruded from a supply station to an extruder and repeatedly weighing the supply station to calculate the throughput of the extruder. The initial line speed necessary to produce a predetermined weight/meter of extrudate is calculated and the line speed is adjusted accordingly. Subsequently, the throughput and the line speed are increased simultaneously, such that the weight/meter is maintained substantially constant until any one of a plurality of parameters such as line speed, screw speed, motor load current, extrudate temperature, melt pressure, etc reaches a predetermined maximum value. Thereafter either the line speed or extruder throughput is adjusted such as to maintain the weight/meter of the extrudate substantially constant at the desired value.
U.S. Pat. No. 5,543,105, issued Aug. 6, 1996, to Stummer et al, discloses a method and apparatus for injection molding. The injection molding machine includes a mold formed by a fixed mold half and a movable mold half cooperating with the fixed mold half for defining a mold cavity of the mold and a gate channel leading to the mold cavity. An injection piston is operatively associated with the mold cavity for pressing a melt via the gate channel into the mold cavity. A sensor device detects a melt front of the melt rising upstream of the mold cavity in a conveying direction of the melt at a predetermined detection height. The sensor device includes walls defining a measurement gap disposed at the detection height and extending transversely to the conveying direction of the melt. The measurement gap is at least partially penetrated by a fraction of the melt from the melt front when the melt front rises toward the mold cavity. A measuring device operatively associated with the measurement gap is responsive to a presence of the fraction of the melt in the measurement gap without directly contacting the melt and generates a measurement signal for controlling predetermined parameters of the machine.
U.S. Pat. No. 5,753,273, issued May 19, 1998, to Ratzenberger et al, discloses a system for monitoring and controlling the composition and the plastic deformation of material being processed in a processing machine has at least one measuring arrangement that includes a first pivotable lever connected to the processing machine at a location where the material flows. The first pivotable lever is biased by a force such that the first pivotable lever contacts the material with a force component acting at a right angle onto the surface of the material. A penetration body is connected to the first pivotable lever at an end thereof facing the material. The penetration body has a wedge shape tapered in a direction toward the surface of the material. A first travel sensor for sensing the depth of penetration of the penetration body into the material is provided. The first travel sensor is fixedly connected to the processing machine and cooperates with the first pivotable level at a distance from the penetration body. A second travel sensor for sensing the advancing speed of the material is substantially stationarily connected to the processing machine in the advancing direction of the material. A processing unit for processing signals received from the first and second travel sensors is provided. A control member for controlling the composition of the material is connected to the processing unit.
The above cited prior art does not disclose a system which provides a non-invasive extruder measurement system which may be used with high pressure, high viscosity fluids such as certain types of explosives. The advantages and benefits of solutions to the above described and/or related problems have been long sought without success. Consequently, those skilled in the art will appreciate the present invention that addresses the above and other problems.